April 2003

Research Capsules
Edited by Harrison Wein, Ph.D.

Using Saris To Fight Cholera
Using Plants to Clean Up Arsenic
Older Homes Encourage Walking

Using Saris To Fight Cholera
by Harrison Wein, Ph.D.

A major global health problem may have found its match in a simple piece of cloth. Research supported by NIH's National Institute of Nursing Research (NINR) found that filters made from old cotton saris cut the number of cholera cases in rural Bangladesh villages almost in half. Other inexpensive cloth should work just as well in other parts of the world where cholera is endemic.

Cholera is a waterborne disease that causes severe diarrhea and vomiting, killing thousands of people around the world every year. It was prevalent in the US in the 1800s but has been virtually eliminated in this country by modern sewage and water treatment systems. Unfortunately, it remains common in poor areas around the world that depend on untreated surface water. Boiling water before drinking is the best way to kill the bacteria that cause the disease, but fuel wood in places like rural Bangladesh is in short supply and costly. When there is severe flooding, which is common in many areas, building fires to boil water is simply not possible.

The bacteria that cause cholera often live attached to plankton, with each plankton carrying up to 10,000 of the tiny bacteria. An international research team led by scientists at the University of Maryland reasoned that if they could filter enough plankton out of the water, they might also remove enough cholera bacteria to keep people from getting sick.

They first did an electron microscope study and found that one inexpensive piece of sari cloth, folded four to eight times, could create a filter with holes small enough to remove most plankton. They then embarked on a three-year study in 65 villages in rural Bangladesh involving a total of about 133,000 people. They trained families to create and use filters when filling their water-collecting pots, called kalashes, from ponds, canals and rivers. All study participants were guaranteed medical treatment, and stool samples from patients with diarrhea were tested for the presence of cholera bacteria.

Cholera rates were reduced by almost half when people filtered their water. Cultural barriers didn't prevent the villagers from filtering their water according to instructions; about 90% followed the procedure. This simple preventive measure has the potential to make a significant impact on a global health problem.

— a report from The NIH Word on Health, April 2003
Proceedings of the National Academy of Sciences 100,3:1051-1055

For information about cholera and how travelers can avoid the disease, visit http://www.cdc.gov/ncidod/dbmd/diseaseinfo/cholera_g.htm at the National Center for Infectious Diseases, part of the Centers for Disease Control and Prevention (not a part of NIH).

Using Plants to Clean Up Arsenic
by Harrison Wein, Ph.D.

Arsenic pollution is a serious health problem, affecting hundreds of millions of people around the world. The methods currently used to clean this element from contaminated soil are expensive and inefficient. A team of scientists supported by NIH's National Institute of General Medical Sciences (NIGMS) have developed a method using plants that has the potential to be easier and more economical.

Arsenic is found naturally in soil and groundwater, but it is spread further through the environment by pesticide use, mining operations and other industrial activities. Arsenic is a poison, as you may know if you're a mystery fan, and high levels can cause an array of health problems like sore throat, nausea, vomiting and death. It has also been linked to many types of cancers, including lung, skin, bladder, liver and kidney.

Arsenic is toxic to most plants, just as it is to animals, but a team of scientists centered at Wayne State University School of Medicine in Detroit and the University of Georgia in Athens believed they could use genetic engineering to create plants that could clean contaminated soil of arsenic, a process called phytoremediation (phyto means plant). To do this, they took two genes from the bacterium Escherichia coli that allow it to grow in the presence of arsenic and put them into the small mustard weed Arabidopsis thaliana, a plant commonly used for genetic engineering.

The resulting plants grow well in the presence of arsenic and, because of the way they have been designed to process the arsenic, are able to accumulate it in their leaves. This is a necessary step if the plants are to be used for phytoremediation. Leaves rich in arsenic can be harvested relatively easily and disposed of safely.

An important aspect of the new technique is that it may be applicable to a wide variety of plant species able to grow in different environments. It holds great promise for improving human health, especially in developing countries where arsenic pollution affects so many people.

— a report from The NIH Word on Health, April 2003
Nature Biotechnology 20:1140-1145

For more information on arsenic, visit the MEDLINEplus information page on arsenic at http://www.nlm.nih.gov/medlineplus/arsenic.html. MEDLINEplus is a service of NIH's National Library of Medicine.

Older Homes Encourage Walking
by Carol Torgan, Ph.D.

As the number of Americans who are sedentary and overweight continues to grow at an alarming rate, health professionals are trying to take a broader look at what factors shape our physical activity choices. One relatively new avenue of research focuses on understanding the environmental factors that encourage physical activity. The surprising finding of one recent study is that people are more likely to walk if they live in an older home.

Drs. David Berrigan and Richard Troiano, researchers from NIH's National Cancer Institute (NCI), took an intriguing look at data from the Third National Health and Nutrition Examination Survey (NHANES III), a nationally representative sample of the U.S. population. They examined the association between home age and walking behavior in over 14,000 adults. Homes were placed into three categories according to when they were built: before 1946, 1946-1973, and 1974-present. Walking patterns were determined by questions such as, "In the past month, how often did you walk a mile or more at a time without stopping?"

Adults who lived in homes built before 1974 in either urban or suburban areas were more likely to walk one or more miles twenty or more times per month than residents of homes built in 1974 or later. Home age didn't influence walking activity for people in rural counties. Home age was not associated with other activities such as jogging, running, swimming, weight lifting, or dancing.

The researchers believe that the explanation for their finding is that older urban and suburban homes are typically in neighborhoods that have more sidewalks, networks of streets, and a combination of business and residential uses. They conclude that community planning decisions can have an influence on physical activity levels and therefore on the health of the population. So although a health club nearby may encourage exercise, it can also help to have tree-lined sidewalks right outside the front door.

— a report from The NIH Word on Health, April 2003
Am J Prev Med 23(2S):74-79, 2002

For information about starting a walking program, see the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) booklet Walking….A step in the Right Direction at: http://www.niddk.nih.gov/health/nutrit/walking/walkingbro/walking.htm.

To learn more about how community design influences physical activity choices, visit the web site of Active Community Environments (ACEs), an initiative sponsored by the Centers for Disease Control and Prevention (CDC), at http://www.cdc.gov/nccdphp/dnpa/aces.htm.